Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 9ad37b9..be01a4d 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Context tracking: Probe on high level context boundaries such as kernel
  * and userspace. This includes syscalls and exceptions entry/exit.